Some of the thermocouples are intended to measure the temperature of the coolant of the reactor, at the outlet of the core, below the upper plate of the core, near the upper end-piece of the fuel assemblies.
The thermocouples inserted into the pipes are subjected to high temperature and pressure stresses, such that some of them may have operating defects after a certain residence time in the back of the reactor.
Thus, it is no longer possible to have a reliable and representative image of the actual temperature of the coolant of the reactor core.
It is therefore necessary to replace these thermocouples and/or these pipes during scheduled upkeep operations of the nuclear reactor.
These pipes are replaced after the reactor has been stopped and cooled and after the cover has been disassembled.
The pipes are generally connected to each other by locking devices. These devices make it possible to lock the pipes in position relative to one another, so as to avoid any contact between the pipes. Such contacts may lead to piercing of the pipes.
The known locking devices are staples welded on the pipes. To replace the defective pipe, it is necessary to place the staples. This placement is a long and complex operation. It may destroy other pipes connected by the staples to the defective pipe.